Graphs are often used to display data. If you look through
newspapers and magazines, you will probably see many graphs
displaying data, from stock market prices to the cost of pizza! There
are many ways to graph data. Some of the most common types of graphs
are line graphs, bar graphs, and circle (or "pie") graphs. A bar
graph showing the number of hosts on the internet is shown below:

This bar graph and other interesting statistics about the use of
the net may be found at this web site:

Circles were of great interest to the mathematicians of ancient
times. Over 3500 years ago, the ancient Egyptians discoverd that if
they measured the Circumference of a circle (the distance 'around'
the circle) and then divided this measurement by the diameter (the
distance 'across; the circle) that they would always get
approximately the same number, a little more than 3. From this
calculation of the ratio of Circumference to diameter, we can derive
the formula for finding the Circumference of a circle if you are
given the diameter:. that formula is C=¹d. Some historical
information about ¹ is written below:

"Pi was known by the Egyptians, who calculated it to be
approximately (4/3)^4 which equals 3.1604. The earliest known
reference to pi occurs in a Middle Kingdom papyrus scroll, written
around 1650 BC by a scribe named Ahmes. He began the scroll with the
words: "The Entrance Into the Knowledge of All Existing Things" and
remarked in passing that he composed the scroll "in likeness to
writings made of old." Towards the end of the scroll, which is
composed of various mathematical problems and their solutions, the
area of a circle is found using a rough sort of pi.

Around 200 BC, Archimedes of Syracuse found that pi is somewhere
about 3.14 (in fractions; Greeks did not have decimals). Pi (which is
a letter in the Greek alphabet) was discovered by a Greek
mathematician named Archimedes. Archimedes wrote a book called The
Measurement of a Circle. In the book he states that Pi is a number
between 3 10/71 and 3 1/7. He figured this out by taking a polygon
with 96 sides and inscribing a circle inside the polygon. That was
Archemedes' concept of Pi."

This information came from the following website, which has many
other interesting facts about the mysterious and intriguing number
called ¹. Why is it called ¹? Because ¹ is the first letter in the
Greek word for circumference.

Many ancient and modern mathematicians have devised ways of
estimating the value of this fascinating number. The Math Forum
website has a feature called "Ask Dr. Math. Anyone send in a math
question, and Dr. Math will answer! Try the link below for a question
related to ¹:

What activities make up your daily life? Collect data on this
topic, and design a circle graph. To collect the data, keep a journal
for one week of how much time you spend on each of your activities:
you might include such categories as sleeping, doing homework, time
spent in class, etc. Organize the data in groups with the hours and
fractions of an hour. You might need to combine some of the smaller
groups into a more general category. You should have at least 8
categories. Now you need to divide the circle into portions for the
categories. For example, if you spend 8 hours sleeping, then that is
eight twenty-fourths of the day, and would then be eight
twenty-fourths of the 360 degrees in a circle. Some example
calculations are shown below:

After calculating the sizes of the sectors of the circle for each
of your daily activities, use a compass (or Geometry software) to
construct a large circle, and draw a circle graph. Measure the angles
using a protractor. Label your graph, using the colorful graph
(called "Age of Users") which is near the top of this page, as an
example.Use colored pens or pencils to color each sector of your
circle graph. Do your best work; make this a beautiful and
informational circle graph!